1. Field of the Invention
The present invention relates to an electromagnetic driving valve of an internal combustion engine for opening and closing an intake and exhaust port of an internal combustion engine.
2. Description of the Prior Art
Conventionally, there has been known an electromagnetic driving valve for driving a valve portion opening and closing an intake and exhaust port of an internal combustion engine, by an electromagnet. This kind of electromagnetic driving valve is provided with a movable plate connected to a transmission shaft extending to the above of the valve portion, and a pair of electromagnets vertically opposing to each other via the movable plate. The movable plate is sucked due to an electromagnetic force which both of the electromagnets alternately generate, thereby moving between both of the electromagnets. Further, when the movable plate is adsorbed to the upper electromagnet, the valve portion closes the intake and exhaust port, and when the movable plate is adsorbed to the lower electromagnet, the valve portion opens the intake and exhaust port.
In this kind of electromagnetic driving valve, an electromagnetic force applied to the movable plate from each of the electromagnets becomes smaller when a distance between the movable plate and the electromagnets sucking the movable plate is increased, and it becomes gradually larger in accordance that the movable plate moves close to the electromagnet. Accordingly, since a displacement speed of the movable plate is increased in accordance that the movable plate moves close to the electromagnet, and the valve portion quickly sits on the intake and exhaust port in accordance therewith, there is a disadvantage that an impact sound and a vibration are generated at a time of closing the valve.
Further, the transmission shaft is separated into a first transmission shaft extended from the valve portion for absorbing an elongation due to a thermal expansion or the like and a second transmission shaft supporting the movable plate. At this time, a spring for urging the valve portion in a valve closing direction is provided in the first transmission shaft. Further, when the movable plate is adsorbed to the upper electromagnet, the valve portion is closed due to the urging force of the spring and a gap on the basis of the thermal expansion or the like is formed between both of the transmission shafts. Further, when the movable plate moves apart from the upper electromagnet, the second transmission shaft is brought into contact with the first transmission shaft, and opens the valve portion against the urging force of the spring. Accordingly, when the movable plate moves apart from the upper electromagnet toward the lower electromagnet at a time of a valve opening operation, there is a disadvantage that the second transmission shaft comes into contact with the first transmission shaft, whereby the impact sound and the vibration are also generated from a contact portion between both of the transmission shafts.
The present invention is made so as to solve the disadvantages mentioned above, and an object of the present invention is to provide an electromagnetic driving valve of an internal combustion engine provided with a significantly compact shock absorbing means which can reduce an impact sound and a vibration in a contact portion between a first transmission shaft and a second transmission shaft and reduce an impact sound and a vibration generated at a time when a valve portion sits on an intake and exhaust port at a time of closing a valve.
In order to achieve the object mentioned above, in accordance with the present invention, there is provided an electromagnetic driving valve of an internal combustion engine comprising:
a valve portion moving in contact with and apart from an intake and exhaust port of the internal combustion engine so as to open and close an intake and exhaust passage;
a first transmission shaft extended from the valve portion toward the above;
a second transmission shaft extended on the same axis of the first transmission shaft so as to move according to a movement of the first transmission shaft;
a pair of electromagnets to which said second transmission is inserted, and opposing to each other in a vertical direction with keeping a gap in an axial direction of the second transmission shaft;
a movable plate provided in the second transmission shaft positioned between both of the electromagnets and moving between both of the electromagnets in correspondence to a magnetic suction between both of the electromagnets, thereby opening and closing the valve portion via the second transmission shaft and the first transmission shaft; and
a pair of spring members provided so as to vertically oppose to each other via both of the electromagnets and urging the first transmission shaft and the second transmission shaft in respectively opposing directions so as to hold the movable plate and the valve body at a predetermined position,
wherein a shock absorbing means provided in the electromagnetic driving valve comprises:
a contact connecting means connected to an upper end of the first transmission shaft and freely extending and compressing while maintaining a contact with a lower end of the second transmission shaft; and
a fluid receiving portion slidably inserting the contact connecting means thereto and gradually discharging a fluid charged in an inner portion thereof together with an upward movement of the contact connecting means at a time of a valve closing operation of the valve portion, thereby reducing a valve closing speed of the valve portion via the first transmission shaft.
In accordance with the present invention, since the extensible contact connecting means is provided between the upper end of the first transmission shaft and the lower end of the second transmission shaft, even when an extension due to a thermal expansion is generated in the first transmission shaft or the second transmission shaft, the contact connecting means is compressed so as to absorb the extension of the first transmission shaft and the second transmission shaft, whereby it is possible to maintain the contact connecting state between the first transmission shaft and the second transmission shaft.
In this case, when the movable plate is sucked by the upper electromagnet, the contact connecting means upward moves within the fluid receiving portion due to an urging force of the lower spring member via the first transmission shaft. At this time, since the fluid charged in an inner portion of the fluid receiving portion is gradually discharged, it is possible to prevent the first transmission shaft from suddenly moving via the contact connecting means due to a fluid discharge resistance. Accordingly, a displacement speed of the valve portion at a time of closing the valve can be sufficiently reduced, and it is possible to reduce a sound and a vibration generated at a time when the valve portion sits on the intake and exhaust port.
Further, when the first transmission shaft and the second transmission shaft move, the contact state between both of the shafts can be maintained via the contact connecting means, so that the collision between the upper end of the first transmission shaft and the lower end of the second transmission shaft can be reduced, and it is possible to reduce the sound and the vibration generated between both of the shafts.
Further, in the shock absorbing means, since the structure is made such that the contact connecting means is inward inserted within the fluid receiving portion, it is possible to form the shock absorbing means which can achieve both of an extension absorption and shock absorption of the first transmission shaft and the second transmission shaft, and a shock absorption at a time of closing the valve portion, in a compact manner.
In accordance with one aspect of the present invention, the contact connecting means comprises:
a cylindrical overcoat member having an upper portion closed by a contact wall brought into contact with a lower end surface of the second transmission shaft;
an inward insertion member inward inserted to the overcoat member slidably and connected to an upper end portion of the first transmission shaft;
a fluid receiving chamber formed between the contact wall within the overcoat member and the inward insertion member;
a fluid introduction passage introducing a fluid to the fluid receiving chamber from an outer portion so as to charge; and
a fluid discharge passage discharging the fluid charged in the fluid receiving chamber in correspondence to a compression of the fluid receiving chamber caused by an expansion of the first transmission shaft or the second transmission shaft.
The fluid is charged into the fluid receiving chamber via the fluid introduction passage, and a state in which the contact wall of the overcoat member is brought into contact with the lower end surface of the second transmission shaft is maintained. In this case, when the extension due to the thermal expansion is generated in the first transmission shaft or the second transmission shaft, the fluid receiving chamber is compressed. Since the fluid is discharged from the fluid discharge passage in accordance therewith, it is possible to smoothly absorb the extension of the first transmission shaft and the second transmission shaft.
At this time, the fluid discharge passage of the contact connecting means is formed between an inner peripheral wall of the overcoat member and an outer peripheral wall of the inward insertion member. Accordingly, when the extension due to the thermal expansion is generated in the first transmission shaft or the second transmission shaft and the fluid receiving chamber is compressed, it is possible to discharge the fluid from a portion between the inner peripheral wall of the overcoat member and the outer peripheral wall of the inward insertion member, so that it is possible to make the structure simple.
Further, it is preferable that a check valve opening in a direction in which the fluid is introduced from the fluid introduction passage and restricting an outflow of the fluid from the fluid introduction passage so as to maintain the fluid in the fluid receiving chamber at a fixed pressure is provided in the fluid receiving chamber of the contact connecting means. Due to the check valve, it is possible to maintain the fluid charged in the fluid receiving chamber at a fixed pressure, and it is possible to securely maintain a state in which the contact wall of the overcoat member is brought into contact with the lower end surface of the second transmission shaft.
As a particular aspect of the check valve, there can be listed up a structure constituted by a check ball provided in the fluid receiving chamber so as to freely open and close the fluid introduction passage, and a spring urging the check ball in a closing direction.
Further, in the aspect, the structure may be made such that the fluid receiving portion is provided with a fluid supplying passage opening at a position above the overcoat member so as to supply the fluid to an inner portion of the fluid receiving portion when the overcoat member of the contact connecting means moves downward within the fluid receiving portion in accordance with the opening operation of the valve portion, and a fluid discharging passage discharging the fluid in the inner portion of the fluid receiving portion to an outer portion from the fluid receiving portion in accordance with an upward movement of the overcoat member at a time of closing operation of the valve portion.
The fluid is charged to the fluid receiving portion via the fluid supplying passage. Accordingly, since a resistance of the charged fluid is generated in the overcoat member moving upward within the fluid receiving portion, it is possible to reduce a speed of the valve portion via the first transmission shaft on the basis of a significantly simple structure.
At this time, it is preferable that the fluid discharging passage of the fluid receiving portion is formed between an inner peripheral wall of the fluid receiving portion and an outer peripheral wall of the overcoat member in the contact connecting means, the fluid receiving portion is provided with a first small diameter portion having an inner diameter smaller than the other portions in an upper end portion thereof, and the overcoat member is provided with a second small diameter portion having an outer diameter smaller than the other portion in correspondence to the first small diameter portion and reducing a discharging amount of the fluid from the fluid discharging passage of the fluid receiving portion in accordance with an upward movement of the overcoat member.
Accordingly, since a diameter of the fluid discharging passage formed between the inner peripheral wall of the fluid receiving portion and the outer peripheral wall of the overcoat member in the contact connecting means is made small when the second small diameter portion moves forward to the first small diameter portion in accordance with the upward movement of the overcoat member within the fluid receiving portion, it is possible to reduce the discharging amount of the fluid immediately before the valve portion is brought into contact with the intake and exhaust port. Accordingly, it is possible to make the structure significantly simple and it is possible to smoothly execute a sudden speed reduction of the valve portion immediately before closing the valve.